System and Method for Modulation Scheme Changes

ABSTRACT

A system and method are disclosed that allow changes of a modulation and coding scheme (MCS) without overhead signaling. A priori, a network device and a user device know the manner in which the MCS will be changed. In one embodiment, the network device indicates the MCS to be used to decode a second portion of a message in a first portion of the message. In another embodiment, the user device blind detects the MCS used over a sub-set of MCSs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.12/341,956 filed Dec. 22, 2008, by Zhijun Cai, et al. entitled “Systemand Method for Modulation Scheme Changes”, (32982-US-PAT; 4214-05401)which claims priority to U.S. Provisional Patent Application No.61/016,646, filed Dec. 26, 2007, by Zhijun Cai, et al. entitled “Systemand Method for Modulation Scheme Changes”, (32982-US-PRV; 4214-05400)which are incorporated by reference herein as if reproduced in theirentirety.

BACKGROUND

In traditional wireless telecommunications systems, transmissionequipment in a base station transmits signals throughout a geographicalregion known as a cell. As technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This advanced network access equipment mightinclude, for example, an enhanced node-B (eNB) rather than a basestation or other systems and devices that are more highly evolved thanthe equivalent equipment in a traditional wireless telecommunicationssystem. Such advanced or next generation equipment is typically referredto as long-term evolution (LTE) equipment. For LTE equipment, the regionin which a wireless device can gain access to a telecommunicationsnetwork might be referred to by a name other than “cell”, such as “hotspot”. As used herein, the term “cell” will be used to refer to anyregion in which a wireless device can gain access to atelecommunications network, regardless of whether the wireless device isa traditional cellular device, an LTE device, or some other device.

Devices that might be used by users in a telecommunications network caninclude both mobile terminals, such as mobile telephones, personaldigital assistants, handheld computers, portable computers, laptopcomputers, tablet computers and similar devices, and fixed terminalssuch as residential gateways, televisions, set-top boxes and the like.Such devices will be referred to herein as user equipment or UE.

Services that might be provided by LTE-based equipment can includebroadcasts or multicasts of television programs, streaming video,streaming audio, and other multimedia content. Such services arecommonly referred to as multimedia broadcast multicast services (MBMS).An MBMS might be transmitted throughout a single cell or throughoutseveral contiguous or overlapping cells. The MBMS may be communicatedfrom an eNB to a UE using point-to-point (PTP) communication orpoint-to-multipoint (PTM) communication.

In wireless communication systems, transmission from the network accessequipment (e.g., eNB) to the UE is referred to as a downlinktransmission. Communication from the UE to the network access equipmentis referred to as an uplink transmission. Wireless communication systemsgenerally require maintenance of timing synchronization to allow forcontinued communications. Maintaining uplink synchronization can beproblematic, wasting throughput and/or decreasing battery life of an UEgiven that a UE may not always have data to transmit.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is an illustration of a cellular network according to anembodiment of the disclosure.

FIG. 2 is an illustration of a cell in a cellular network according toan embodiment of the disclosure.

FIG. 3 is the cumulative density function (CDF) of user geometry in acell.

FIG. 4 is an illustrative block diagram of a message in accordance withone embodiment of the present invention.

FIG. 5 is an illustrative block diagram of a network access equipment.

FIG. 6 is an illustrative block diagram of a user equipment

FIG. 7 is a flow chart corresponding to one network access equipmentembodiment.

FIG. 8 is a flow chart corresponding to a user equipment embodiment.

FIG. 9 is an illustration of an MCS choice scheme.

FIG. 10 is a flow chart corresponding to another aspect of a networkaccess equipment embodiment.

FIG. 11 is an illustrative block diagram of a network access equipment.

FIG. 12 is a flow chart corresponding to another aspect of a userequipment embodiment.

FIG. 13 is a flow chart corresponding to another aspect of a networkaccess equipment embodiment.

FIG. 14 is a flow chart corresponding to another aspect of a userequipment embodiment.

FIG. 15 is a diagram of a wireless communications system including amobile device operable for some of the various embodiments of thedisclosure.

FIG. 16 is a block diagram of a mobile device operable for some of thevarious embodiments of the disclosure.

FIG. 17 is a diagram of a software environment that may be implementedon a mobile device operable for some of the various embodiments of thedisclosure.

FIG. 18 is an exemplary general purpose computer according to oneembodiment of the present disclosure.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents.

FIG. 1 illustrates an exemplary cellular network 100 according to anembodiment of the disclosure. The cellular network 100 may include aplurality of cells 102 ₁, 102 ₂, 102 ₃, 102 ₄, 102 ₅, 102 ₆, 102 ₇, 102₈, 102 ₉, 102 ₁₀, 102 ₁₁, 102 ₁₂, 102 ₁₃, and 102 ₁₄ (collectivelyreferred to as cells 102). As is apparent to persons of ordinary skillin the art, each of the cells 102 represents a coverage area forproviding cellular services of the cellular network 100 throughcommunication from a network access equipment (e.g., eNB). While thecells 102 are depicted as having non-overlapping coverage areas, personsof ordinary skill in the art will recognize that one or more of thecells 102 may have partially overlapping coverage with adjacent cells.In addition, while a particular number of the cells 102 are depicted,persons of ordinary skill in the art will recognize that a larger orsmaller number of the cells 102 may be included in the cellular network100.

One or more UEs 10 may be present in each of the cells 102. Althoughonly one UE 10 is depicted and is shown in only one cell 102 ₁₂, it willbe apparent to one of skill in the art that a plurality of UEs 10 may bepresent in each of the cells 102. A network access equipment 20 in eachof the cells 102 performs functions similar to those of a traditionalbase station. That is, the network access equipments 20 provide a radiolink between the UEs 10 and other components in a telecommunicationsnetwork. While the network access equipment 20 is shown only in cell 102₁₂, it should be understood that network access equipment would bepresent in each of the cells 102. A central control 110 may also bepresent in the cellular network 100 to oversee some of the wireless datatransmissions within the cells 102.

FIG. 2 depicts a more detailed view of the cell 102 ₁₂. The networkaccess equipment 20 in cell 102 ₁₂ may promote communication via atransmitter 27, a receiver 29, and/or other well known equipment.Similar equipment might be present in the other cells 102. A pluralityof UEs 10 are present in the cell 102 ₁₂, as might be the case in theother cells 102. In the present disclosure, the cellular systems orcells 102 are described as engaged in certain activities, such astransmitting signals; however, as will be readily apparent to oneskilled in the art, these activities would in fact be conducted bycomponents comprising the cells.

In each cell, the transmissions from the network access equipment 20 tothe UEs 10 are referred to as downlink transmissions, and thetransmissions from the UEs 10 to the network access equipment 20 arereferred to as uplink transmissions. The UE may include any device thatmay communicate using the cellular network 100. For example, the UE mayinclude devices such as a cellular telephone, a laptop computer, anavigation system, or any other devices known to persons of ordinaryskill in the art that may communicate using the cellular network 100.

Wireless communication systems use modulation and coding to compensatefor varying channel conditions and payload variances. There are manytypes of modulation and coding schemes. For example, there is amplitudemodulation and phase modulation. There are also different levels ofmodulation for example 16 QAM (Quadrature Amplitude Modulation) and 64QAM. Further, there are different types of coding. There are rate 1/3codes and rate 1/2 codes. For a rate 1/3 code on average, three codedbits are used to send one information bit, while in a rate 1/2 code, onaverage, two coded bits are used to send one information bit. As aresult, different modulation and coding schemes will provide for adifferent amount of raw information data to be sent using the sameresource. For example, a rate 1/2 coding scheme will allow moreinformation bits to be sent over the same time period in the samebandwidth than a rate 1/3 coding scheme, assuming the same modulationscheme is applied with both coding schemes. Further, the use ofdifferent modulation schemes will also result in more or less rawinformation data transmitted depending on the modulation scheme used.The various coding schemes provide redundancy in the data, thus over anoisy channel a more redundant coding scheme may allow the data to bedecoded and thus received correctly, while a less redundant codingscheme may be un-decodable over the same channel.

In order for communication from a network access equipment to a UE to beproperly received, the network access equipment must encode the datausing a modulation and coding scheme (MCS), and the UE must decode thedata using the same MCS. This requires that the UE know what MCS to use.In prior art systems, the network access equipment communicates the MCSto the UE via overhead signaling. For example, the network accessequipment may communicate the MCS to the UE using the physical downlinkcontrol channel (PDCCH).

In semi-persistent scheduled services, e.g., voice over internetprotocol (VoIP), some resources are allocated persistently, so that theUE does not incur additional signaling such as scheduling grants,modulation and coding information, etc. However, due to changing channelconditions and payload size variance, it may be desirable to allow thechange of the modulation and coding in order to more efficiently utilizethe radio resources.

In one embodiment, the UE can blind-detect all possible modulation andcoding schemes. That is, the network access equipment can choose whichMCS to use, and the UE will attempt to decode a received message usingall known MCSs. However, attempting to decode a received message usingall known MCSs would increase the processing power and time required bythe UE to decode the message. This implementation could also reducebattery life.

FIG. 3 is the cumulative density function (CDF) of user geometry in acell. As can be seen from FIG. 3, the dynamic range of a user's averagesignal to noise ratio (SNR) is large, e.g., −4.2 dB at 95% coverage(cell edge) and 13 dB at 10% (close to the network access equipment). Ifusers at the cell edge and users close to the network access equipmentcould use the same modulation and coding scheme, the spectrum efficiencycould be reduced. For example, if the same quadrature phase shift key(QPSK) and rate 1/4 coding is used for all users, the spectrumefficiency is 0.5 bits/symbol. If the payload is 244 bits, then 488symbols are required for the transmission. This may be suitable for thecell edge user case (e.g., low geometry case). However, if the same MCSis used for the users close to the network access equipment (e.g., thehigh geometry case), then significant resources are wasted. For the 10thpercentile users, 16-quadrature amplitude modulation (16-QAM) and 3/4coding may be used, which provides 3 bits/symbol. Thus, only 82 symbolsare required to transmit the 244 bit payload. This provides a factor of6 times savings. Additionally, if 64-QAM is utilized, additional savingsare achieved. These savings are even more pronounced on the uplink dueto the lack of quick resource control from the network access equipment.

In some communications systems, it may not be necessary to rapidlychange the MCS. The hybrid automatic repeat request (HARQ) cancompensate for most of the fast fading effects so there is little needfor fast AMC (Adaptive Modulation and Coding) based on a channel qualityindictor (CQI) to deal with the small near-constant size payload. By notrapidly changing the MCS, the associated VoIP overhead can be reducedand the battery life of the UE can be conserved. However, the UE mayneed to slowly change its MCS based on the average SNR (e.g., movingfrom cell center to cell edge) or codec rate changes (e.g., 12.2 kchanges to 4.8 k). Some of these changes may also affect the scheduledresource size (e.g., number of resource blocks (RBs)) and position ofthe resources in the sub-frames.

As shown in FIG. 4, in one embodiment, a network access equipmentindicates to a UE a new MCS using a message 401 divided into a firstportion 403 and a second portion 405. In one implementation, the firstportion 403 could be header bits; however, other portions of the messagecould be used as well. The first portion 403 is encoded with a MCS knownboth to the network access equipment and to the UE. The UE can decodethe first portion without having to blind-detect the MCS. The firstportion 403 provides instructions 407 to the UE of a MCS to use todecode the second portion 405. The network access equipment encodes thesecond portion 405 with the MCS that was provided in the first portion403. The network access equipment then sends the message.

FIG. 5 illustrates modules within the network access equipment. Thesemodules are for illustrative purposes and may be stored in any memory orprocessor within the network access equipment. Additionally, thesemodules may be implemented in software, hardware or firmware. Within thenetwork access equipment 20, is an encoder module 501 and a transmissionmodule 503. These modules will be discussed in conjunction to the methodflow diagram shown in FIG. 7. The encoder module 501, at block 701,encodes a first portion of the message 403 using a known MCS. Then atblock 703, the encoder module 501 provides an instruction 407 in thefirst portion 403 of a MCS to use to decode the second portion 405. Atblock 705, the encoder module 501 encodes the second portion of themessage 405 using the instructed MCS. The encoder module 501 then sendsthe message to the transmission module 503. At block 707, thetransmission module sends the message.

FIG. 6 illustrates modules within the UE 10. These modules are forillustrative purposes and may be stored in any memory or processorwithin the UE. Additionally, these modules may be implemented insoftware, hardware or firmware. The UE 10 includes a receiver module 601and a decoder module 603. These modules will be discussed in conjunctionwith the method flow diagram shown in FIG. 8. At block 801, the receivermodule 601 receives the encoded message. Then the receiver module 601passes the message to the decoder module 603. At block 803, the decodermodule 603 decodes the first portion 403 using the known MCS. At block805, the decoder module 603 then retrieves the instructed MCS 407 fromthe first portion 403 to use to decode the second portion 405. At block807, the decoder module 603 decodes the second portion 405 of themessage using the instructed MCS 407. In some implementations,additional resource blocks for transmission may be necessary with thechange in MCS. In those implementations, the first portion 403 will alsoindicate where in the transmission the user equipment can find theadditional resource blocks for concatenation.

In another embodiment, the network access equipment may only change theMCS within a certain range of MCSs. As shown in FIG. 9, the networkaccess equipment can only use a MCS that is within one increment of thepreviously used MCS. For example, assume in subframe N that the networkaccess equipment transmits the voice data to the UE using a MCS index17; then in the subframe N+20 (e.g., the next Voice frame transmission(20 ms apart), and each subframe is 1 ms), the network access equipmentcan only select the MCS 16 (i.e., 17−1), MCS 17, or MCS 18 (i.e., 17+1).The UE will begin by decoding the voice packet with the previous MCS(i.e., 17). If the UE cannot decode the transmission using MCS 17, theUE will try either MCS 16 or 18. As an example, the UE might use MCS 18.If the UE still cannot decode the transmission, the UE will use theother MCS, in this example MCS 16. If the UE is unable to decode thetransmission using MCS 16, MCS 17, or MCS 18, then the UE will send anegative acknowledgement (NACK) on the uplink. One skilled in the artwill appreciate that the foregoing example uses an increment value of 1.However, other increment values can be used. For example, if anincrement value of two is chosen, the possible MCS values would be MCS15, 16, 17, 18 and 19.

Using an increment value may reduce the UE's blind detection range andallow the MCS to gradually change in a larger dynamic range withoutincurring any additional reconfiguration signaling. The limited dynamicrange (e.g., the maximum MCS steps that the transmitter can change inconsecutive transmissions) may be signaled to the UE at the call setupstage for both the uplink and downlink. Therefore, the receiver willblindly detect in a very small MCS range based on the agreed rulecontinuously.

FIG. 10 illustrates a method flow diagram for a network access equipmentwhere the change in MCS can only be within a range of certain MCSs. FIG.11 illustrates modules that could be used to implement the method flowdiagram. These modules are for illustrative purposes and may be storedin any memory or processor within the network access equipment.Additionally, these modules may be implemented in software, hardware orfirmware. Within the network access equipment 20 is a MCS determinationmodule 1101, an encoder module 1103 and a transmission module 1105. Thedescription of these modules will be done in conjunction with the methodflow diagram of FIG. 10.

At block 1001, the MCS determination module 1101 determines a first MCSindex, i, from a first set of N MCS values. At block 1003, the MCSdetermination module 1103 defines an increment value k, where k≧N. Atblock 1005, the transmission module 1105 sends a first message encodedby the encoder module 1103 with the first MCS index value, i, receivedfrom the MCS determination module 1101. Then at block 1007, thetransmission module 1105 sends a second message encoded by the encodermodule 1103 using a second MCS index value j, received from the MCSdetermination module 1101, wherein i−k≦j≦i+k.

FIG. 12 illustrates a method flow diagram for a UE where the change inMCS can only be within a range of certain MCSs. At block 1201, the UEstores a set of N MCS values and increment value k, where k≦N. At block1203, a receive module 601 (shown in FIG. 6), receives a first messageencoded with a first MCS index i. At block 1205, decoder module 603decodes the first message using the first MCS index i. At block 1207,the receiver module 601 receives a second message encoded using a MCSindex value j. At block 1209, the decoder module 603 attempts to decodethe second message using a first MCS index i. At block 1211, the decodermodule 603 chooses a first attempt MCS index, f, where i−k≦f≦i+k. Atblock 1213, the decoder module attempts to decode the second messageusing the first attempt index f. If the decode fails, the decoder modulewill choose an additional attempt index until all the attempt indexesare exhausted. If the decoder still cannot decode the message, in someembodiments, the UE will send a message back to the network accessequipment indicating that the UE was unable to determine the proper MCSto decode the message.

In another embodiment, the network access equipment slowly changes theblind decoding configuration set when certain events occur (e.g., onlywhen the UE's geometry is largely changed or the codec's rate ischanged). Otherwise, the network access equipment will keep the blinddecoding configuration set unchanged. The network access equipment maydetect the variation of channel condition by UE sending CQI in a slowmanner.

In one implementation, at the beginning of call set up, the networkaccess equipment notifies the UE about the indexes for various blinddecoding configuration sets by radio resource control (RRC) signaling(e.g., total 3 blind detection configuration set, indexed set 1, set 2,and set 3). In one implementation, set 1 may comprise three MCSs, e.g.,1, 3 and 5. Set 2 may comprise three different MCSs, e.g., 2, 6, and 7,while set 3 may comprise another three MCSs, e.g., 3, 4, and 6. Thus,the network access equipment signals to the UE that there are threedifferent blind detection configuration sets. The network accessequipment also signals to the UE which set to use initially. The UE willthen blind detect a transmission received from the network accessequipment using only the MCSs in the signaled set. Thus, if the networkaccess equipment signals to the UE to use set 1, the UE will blinddetect the transmission using MCSs 1, 3 and 5.

In one implementation, when an event trigger occurs (e.g., when the UE'sgeometry sufficiently changes), a media access control (MAC) packet dataunit (PDU) is generated to re-configure the blind decoding configurationset by only including the set index. Thus, for example, the networkaccess equipment may generate a signal to the UE containing the indexnumber 2. This index number 2 will indicate to the UE that the networkaccess equipment will now be using MCSs 2, 6 and 7. In some embodiments,a start time of when the network access equipment will begin to use thesecond blind detection configuration set is included in the signalingmessage. This start time may be an absolute start time (i.e., a framecount indication), or it may be a relative start time (i.e., providing acountdown/count-up timer). An absolute start time will be independent ofwhen the signaling message is received at the user equipment, while arelative start time is dependent upon when the signaling message isreceived.

FIG. 13 illustrates a method flow diagram of one embodiment of thenetwork access equipment. At block 1301, the transmission module 1105(shown in FIG. 11) sends an indication to use a first blind detectionconfiguration set. At block 1303, the MCS determination module 1103chooses a MCS from the first blind detection configuration set. At block1305, the encoder module 1103 encodes the data in accordance with thechosen MCS from the first blind detection configuration set. At block1307, the transmission module 1105 sends the encoded data. At block1309, the transmission module 1105 sends an indication to use a secondblind detection configuration set. In one embodiment, the MCSdetermination module 1101 receives an indication that a new MCS isdesired and chooses the second blind detection configuration set. Atblock 1311, the transmission module 1105 sends data encoded with a MCSchosen from the second blind detection configuration set.

In one implementation, the blind detection configuration set size isonly one (i.e., only one MCS is included in the set). The network accessequipment slowly changes the MCS when certain events occur (e.g., onlywhen the UE's geometry changes or the codec's rate is changed).Otherwise, the network access equipment will keep the MCS unchanged.Whenever the MCS changes, the network access equipment notifies the UEabout the change via RRC signaling. In this implementation, the MCS isnot sent for each data packet, but is only sent when a change is tooccur.

FIG. 14 illustrates a method flow diagram of one embodiment of the UE.At block 1401, the receive module 601 (shown in FIG. 6) receives anindication to use a first blind detection configuration set. At block1403, the receive module 601 receives data. At block 1405, the decodermodule 603 blind detects which MCS to use to decode the received datafrom the first blind detection configuration set. At block 1407, thereceive module 601, receives an indication to use a second blinddetection configuration set. At block 1409, the receive module 601receives additional data. At block 1411, the decoder module 603 blinddetects which MCS to use to decode the additional received data from thesecond blind detection configuration set.

FIG. 15 illustrates a wireless communications system including anembodiment of the UE 10. The UE 10 is operable for implementing aspectsof the disclosure, but the disclosure should not be limited to theseimplementations. Though illustrated as a mobile phone, the UE 10 maytake various forms including a wireless handset, a pager, a personaldigital assistant (PDA), a portable computer, a tablet computer, or alaptop computer. Many suitable devices combine some or all of thesefunctions. In some embodiments of the disclosure, the UE 10 is not ageneral purpose computing device like a portable, laptop or tabletcomputer, but rather is a special-purpose communications device such asa mobile phone, a wireless handset, a pager, a PDA, or atelecommunications device installed in a vehicle. In another embodiment,the UE 10 may be a portable, laptop or other computing device. The UE 10may support specialized activities such as gaming, inventory control,job control, and/or task management functions, and so on.

The UE 10 includes a display 402. The UE 10 also includes atouch-sensitive surface, a keyboard or other input keys generallyreferred as 404 for input by a user. The keyboard may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY, andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include atrackwheel, an exit or escape key, a trackball, and other navigationalor functional keys, which may be inwardly depressed to provide furtherinput function. The UE 10 may present options for the user to select,controls for the user to actuate, and/or cursors or other indicators forthe user to direct.

The UE 10 may further accept data entry from the user, including numbersto dial or various parameter values for configuring the operation of theUE 10. The UE 10 may further execute one or more software or firmwareapplications in response to user commands. These applications mayconfigure the UE 10 to perform various customized functions in responseto user interaction. Additionally, the UE 10 may be programmed and/orconfigured over-the-air, for example from a wireless base station, awireless access point, or a peer UE 10.

Among the various applications executable by the UE 10 are a webbrowser, which enables the display 402 to show a web page. The web pagemay be obtained via wireless communications with a wireless networkaccess node, a cell tower, a peer UE 10, or any other wirelesscommunication network or system 400. The network 400 is coupled to awired network 408, such as the Internet. Via the wireless link and thewired network, the UE 10 has access to information on various servers,such as a server 410. The server 410 may provide content that may beshown on the display 402. Alternately, the UE 10 may access the network400 through a peer UE 10 acting as an intermediary, in a relay type orhop type of connection.

FIG. 16 shows a block diagram of the UE 10. While a variety of knowncomponents of UEs 10 are depicted, in an embodiment a subset of thelisted components and/or additional components not listed may beincluded in the UE 10. The UE 10 includes a digital signal processor(DSP) 502 and a memory 504. As shown, the UE 10 may further include anantenna and front end unit 506, a radio frequency (RF) transceiver 508,an analog baseband processing unit 510, a microphone 512, an earpiecespeaker 514, a headset port 516, an input/output interface 518, aremovable memory card 520, a universal serial bus (USB) port 522, ashort range wireless communication sub-system 524, an alert 526, akeypad 528, a liquid crystal display (LCD), which may include a touchsensitive surface 530, an LCD controller 532, a charge-coupled device(CCD) camera 534, a camera controller 536, and a global positioningsystem (GPS) sensor 538. In an embodiment, the UE 10 may include anotherkind of display that does not provide a touch sensitive screen. In anembodiment, the DSP 502 may communicate directly with the memory 504without passing through the input/output interface 518.

The DSP 502 or some other form of controller or central processing unitoperates to control the various components of the UE 10 in accordancewith embedded software or firmware stored in memory 504 or stored inmemory contained within the DSP 502 itself. In addition to the embeddedsoftware or firmware, the DSP 502 may execute other applications storedin the memory 504 or made available via information carrier media suchas portable data storage media like the removable memory card 520 or viawired or wireless network communications. The application software maycomprise a compiled set of machine-readable instructions that configurethe DSP 502 to provide the desired functionality, or the applicationsoftware may be high-level software instructions to be processed by aninterpreter or compiler to indirectly configure the DSP 502.

The antenna and front end unit 506 may be provided to convert betweenwireless signals and electrical signals, enabling the UE 10 to send andreceive information from a cellular network or some other availablewireless communications network or from a peer UE 10. In an embodiment,the antenna and front end unit 506 may include multiple antennas tosupport beam forming and/or multiple input multiple output (MIMO)operations. As is known to those skilled in the art, MIMO operations mayprovide spatial diversity which can be used to overcome difficultchannel conditions and/or increase channel throughput. The antenna andfront end unit 506 may include antenna tuning and/or impedance matchingcomponents, RF power amplifiers, and/or low noise amplifiers.

The RF transceiver 508 provides frequency shifting, converting receivedRF signals to baseband and converting baseband transmit signals to RF.In some descriptions a radio transceiver or RF transceiver may beunderstood to include other signal processing functionality such asmodulation/demodulation, coding/decoding, interleaving/deinterleaving,spreading/despreading, inverse fast Fourier transforming (IFFT)/fastFourier transforming (FFT), cyclic prefix appending/removal, and othersignal processing functions. For the purposes of clarity, thedescription here separates the description of this signal processingfrom the RF and/or radio stage and conceptually allocates that signalprocessing to the analog baseband processing unit 510 and/or the DSP 502or other central processing unit. In some embodiments, the RFTransceiver 508, portions of the Antenna and Front End 506, and theanalog baseband processing unit 510 may be combined in one or moreprocessing units and/or application specific integrated circuits(ASICs).

The analog baseband processing unit 510 may provide various analogprocessing of inputs and outputs, for example analog processing ofinputs from the microphone 512 and the headset 516 and outputs to theearpiece 514 and the headset 516. To that end, the analog basebandprocessing unit 510 may have ports for connecting to the built-inmicrophone 512 and the earpiece speaker 514 that enable the UE 10 to beused as a cell phone. The analog baseband processing unit 510 mayfurther include a port for connecting to a headset or other hands-freemicrophone and speaker configuration. The analog baseband processingunit 510 may provide digital-to-analog conversion in one signaldirection and analog-to-digital conversion in the opposing signaldirection. In some embodiments, at least some of the functionality ofthe analog baseband processing unit 510 may be provided by digitalprocessing components, for example by the DSP 502 or by other centralprocessing units.

The DSP 502 may perform modulation/demodulation, coding/decoding,interleaving/deinterleaving, spreading/despreading, inverse fast Fouriertransforming (IFFT)/fast Fourier transforming (FFT), cyclic prefixappending/removal, and other signal processing functions associated withwireless communications. In an embodiment, for example in a codedivision multiple access (CDMA) technology application, for atransmitter function the DSP 502 may perform modulation, coding,interleaving, and spreading, and for a receiver function the DSP 502 mayperform despreading, deinterleaving, decoding, and demodulation. Inanother embodiment, for example in an orthogonal frequency divisionmultiplex access (OFDMA) technology application, for the transmitterfunction the DSP 502 may perform modulation, coding, interleaving,inverse fast Fourier transforming, and cyclic prefix appending, and fora receiver function the DSP 502 may perform cyclic prefix removal, fastFourier transforming, deinterleaving, decoding, and demodulation. Inother wireless technology applications, yet other signal processingfunctions and combinations of signal processing functions may beperformed by the DSP 502.

The DSP 502 may communicate with a wireless network via the analogbaseband processing unit 510. In some embodiments, the communication mayprovide Internet connectivity, enabling a user to gain access to contenton the Internet and to send and receive e-mail or text messages. Theinput/output interface 518 interconnects the DSP 502 and variousmemories and interfaces. The memory 504 and the removable memory card520 may provide software and data to configure the operation of the DSP502. Among the interfaces may be the USB interface 522 and the shortrange wireless communication sub-system 524. The USB interface 522 maybe used to charge the UE 10 and may also enable the UE 10 to function asa peripheral device to exchange information with a personal computer orother computer system. The short range wireless communication sub-system524 may include an infrared port, a Bluetooth interface, an IEEE 802.11compliant wireless interface, or any other short range wirelesscommunication sub-system, which may enable the UE 10 to communicatewirelessly with other nearby mobile devices and/or wireless basestations.

The input/output interface 518 may further connect the DSP 502 to thealert 526 that, when triggered, causes the UE 10 to provide a notice tothe user, for example, by ringing, playing a melody, or vibrating. Thealert 526 may serve as a mechanism for alerting the user to any ofvarious events such as an incoming call, a new text message, and anappointment reminder by silently vibrating, or by playing a specificpre-assigned melody for a particular caller.

The keypad 528 couples to the DSP 502 via the interface 518 to provideone mechanism for the user to make selections, enter information, andotherwise provide input to the UE 10. The keyboard 528 may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include atrackwheel, an exit or escape key, a trackball, and other navigationalor functional keys, which may be inwardly depressed to provide furtherinput function. Another input mechanism may be the LCD 530, which mayinclude touch screen capability and also display text and/or graphics tothe user. The LCD controller 532 couples the DSP 502 to the LCD 530.

The CCD camera 534, if equipped, enables the UE 10 to take digitalpictures. The DSP 502 communicates with the CCD camera 534 via thecamera controller 536. In another embodiment, a camera operatingaccording to a technology other than Charge Coupled Device cameras maybe employed. The GPS sensor 538 is coupled to the DSP 502 to decodeglobal positioning system signals, thereby enabling the UE 10 todetermine its position. Various other peripherals may also be includedto provide additional functions, e.g., radio and television reception.

FIG. 17 illustrates a software environment 602 that may be implementedby the DSP 502. The DSP 502 executes operating system drivers 604 thatprovide a platform from which the rest of the software operates. Theoperating system drivers 604 provide drivers for the wireless devicehardware with standardized interfaces that are accessible to applicationsoftware. The operating system drivers 604 include applicationmanagement services (“AMS”) 606 that transfer control betweenapplications running on the UE 10. Also shown in FIG. 17 are a webbrowser application 608, a media player application 610, and Javaapplets 612. The web browser application 608 configures the UE 10 tooperate as a web browser, allowing a user to enter information intoforms and select links to retrieve and view web pages. The media playerapplication 610 configures the UE 10 to retrieve and play audio oraudiovisual media. The Java applets 612 configure the UE 10 to providegames, utilities, and other functionality. A component 614 might providefunctionality related to the present disclosure.

The UEs 10, eNBs 20, and central control 110 of FIG. 1 and othercomponents that might be associated with the cells 102 may include anygeneral-purpose computer with sufficient processing power, memoryresources, and network throughput capability to handle the necessaryworkload placed upon it. FIG. 18 illustrates a typical, general-purposecomputer system 700 that may be suitable for implementing one or moreembodiments disclosed herein. The computer system 700 includes aprocessor 720 (which may be referred to as a central processor unit orCPU) that is in communication with memory devices including secondarystorage 750, read only memory (ROM) 740, random access memory (RAM) 730,input/output (I/O) devices 700, and network connectivity devices 760.The processor may be implemented as one or more CPU chips.

The secondary storage 750 is typically comprised of one or more diskdrives or tape drives and is used for non-volatile storage of data andas an over-flow data storage device if RAM 730 is not large enough tohold all working data. Secondary storage 750 may be used to storeprograms which are loaded into RAM 730 when such programs are selectedfor execution. The ROM 740 is used to store instructions and perhapsdata which are read during program execution. ROM 740 is a non-volatilememory device which typically has a small memory capacity relative tothe larger memory capacity of secondary storage. The RAM 730 is used tostore volatile data and perhaps to store instructions. Access to bothROM 740 and RAM 730 is typically faster than to secondary storage 750.

I/O devices 700 may include printers, video monitors, liquid crystaldisplays (LCDs), touch screen displays, keyboards, keypads, switches,dials, mice, track balls, voice recognizers, card readers, paper tapereaders, or other well-known input devices.

The network connectivity devices 760 may take the form of modems, modembanks, ethernet cards, universal serial bus (USB) interface cards,serial interfaces, token ring cards, fiber distributed data interface(FDDI) cards, wireless local area network (WLAN) cards, radiotransceiver cards such as code division multiple access (CDMA) and/orglobal system for mobile communications (GSM) radio transceiver cards,and other well-known network devices. These network connectivity 760devices may enable the processor 720 to communicate with an Internet orone or more intranets. With such a network connection, it iscontemplated that the processor 720 might receive information from thenetwork, or might output information to the network in the course ofperforming the above-described method steps. Such information, which isoften represented as a sequence of instructions to be executed usingprocessor 720, may be received from and outputted to the network, forexample, in the form of a computer data signal embodied in a carrierwave.

Such information, which may include data or instructions to be executedusing processor 720 for example, may be received from and outputted tothe network, for example, in the form of a computer data baseband signalor signal embodied in a carrier wave. The baseband signal or signalembodied in the carrier wave generated by the network connectivity 760devices may propagate in or on the surface of electrical conductors, incoaxial cables, in waveguides, in optical media, for example opticalfiber, or in the air or free space. The information contained in thebaseband signal or signal embedded in the carrier wave may be orderedaccording to different sequences, as may be desirable for eitherprocessing or generating the information or transmitting or receivingthe information. The baseband signal or signal embedded in the carrierwave, or other types of signals currently used or hereafter developed,referred to herein as the transmission medium, may be generatedaccording to several methods well known to one skilled in the art.

The processor 720 executes instructions, codes, computer programs,scripts which it accesses from hard disk, floppy disk, optical disk(these various disk-based systems may all be considered secondarystorage 750), ROM 740, RAM 730, or the network connectivity devices 760.While only one processor 720 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as executed by aprocessor, the instructions may be executed simultaneously, serially, orotherwise executed by one or multiple processors.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

1. A method for signaling modulation and coding schemes (MCSs)comprising: determining a first MCS index i from a set of N MCS values;defining an increment value k, where k is less than N; sending a firstmessage encoded by the first MCS index; and sending a second messageencoded by a second MCS index j, where i−k is less than or equal to jwhich is less than or equal to i+k.
 2. The method of claim 1 furthercomprising sending the increment value k.
 3. The method of claim 1,wherein the second MCS index j is selected based upon channelconditions.
 4. A method for changing modulation and coding schemes(MCSs) comprising: storing a set of N MCS values and an increment valuek, where k is less than N; receiving a first message encoded with afirst MCS index i; decoding the first message using the first MCS indexi; receiving a second message encoded with a second MCS index;attempting to decode the second message using the first MCS index i;choosing a first attempt MCS index, the first attempt MCS index beinggreater than or equal to i−k and less than or equal to i+k; andattempting to decode the second message using the first attempt MCSindex.
 5. The method of claim 4 further comprising receiving theincrement value k.
 6. The method of claim 4 further comprising: whendecoding the second message fails using the first attempt MCS index,attempting to decode the second message using a second attempt MCSindex.
 7. The method of claim 6 further comprising: when decoding thesecond message fails using the second attempt MCS index, attempting todecide the second message using another attempt MCS index from the setof N MCS values.
 8. The method of claim 7 further comprising: whendecoding the second message fails N times, wherein N different attemptMCS indexes are used, sending a message indicating that a proper MCScould not be determined.
 9. The method of claim 4, wherein a maximumnumber of attempt MCS indexes is equal to N.
 10. A network devicecomprising: a modulation and coding scheme (MCS) determination moduleconfigured to determine a first MCS index i from a set of N MCS values;the MCS determination module further configured to define an incrementvalue k, where k is less than N; and a transmission module configured tosend a first message encoded by the first MCS index i and send a secondmessage encoded by a second MCS index j, where i−k is less than or equalto j which is less than or equal to i+k.
 11. The network device of claim10 wherein the transmission module is further configured to send theincrement value k.
 12. The network device of claim 10, wherein thesecond MCS index j is selected based upon channel conditions.
 13. A userequipment comprising: a memory configured to store a set of N modulationand coding scheme (MCS) values and an increment value k, where k is lessthan N; a receive module configured to: receive a first message encodedwith a first MCS index i; receive a second message encoded with a secondMCS index j; and a decoder module configured to: decode the firstmessage using the first MCS index i; attempt to decode the secondmessage using the first MCS index i; choose a first attempt MCS indexfrom the set of N modulation and coding schemes, the first attempt MCSindex being greater than or equal to i−k and less than or equal to i+k;and decode the second message using the first attempt MCS index.
 14. Theuser equipment of claim 13 wherein the receive module is furtherconfigured to receive the increment value k.
 15. The user equipment ofclaim 13 wherein the decoder module is further configured to: whendecoding the second message fails using the first attempt MCS index,attempt to decode the second message using a second attempt MCS index.16. The user equipment of claim 15, wherein the decoder module isfurther configured to: when decoding the second message fails using thesecond attempt MCS index, attempting to decode the second message usinganother attempt MCS index from the set of N MCS values.
 17. The userequipment of claim 15 further comprising: a transmission moduleconfigured to, when decoding the second message fails N times, using Ndifferent attempt MCS indexes, send a message indicating that a properMCS could not be determined.
 18. The user equipment of claim 13, whereina maximum number of attempt MCS indexes is equal to N.